Her, you suppose

As much as you're wary about it, Ava seems to love the idea of you changing her over and over to make her into your ideal lover. And as much as you like her slim form, Monica's tits are amazing, and it's not fair for your girlfriend to have the second-best anything of your harem.

...huh, harem. It's not such a bad idea, now that you're thinking about it.

Anyway, you think HER real strongly for a moment and reality snaps back into place.

Your orgasm smacks into you like getting hit by a semi-truck, and you feel a huge blast of cum squirt out of your cock and into your girlfriend. You look down at her, eager despite yourself to see how she's changing.

As you might have guessed, it's her tits. They're growing fatter and fatter before your very eyes, quickly eclipsing cantaloupes and showing no signs of stopping.

Ava's hands are playing with her nipples as she squirms on your cock, her own orgasm coming in waves. "So big... so big..." she moans.

"He is so big! Such a stud!" Monica chimes in, assuming -- wrongly, you're pretty sure -- that Ava is praising your cock, instead of her own growing breasts. Her eyes are glued on your crotch as she idly plays with herself, apparently still a little hungry for more of your massive dick.

Ava is still swelling, though, now easily bigger than Monica, her tits fatter than watermelons and only now even starting to slow down.

As they finally look like they're stopping, you imagine that they'd give your mother a run for her money now. The idea of Ava and your mom kneeling next to each other, massive racks smushed together, battling for supremacy, tongues ready to catch your seed -- your cock throbs at the idea of it.

You step back, your cock sliding easily out of your girlfriend's pussy and slapping heavily against your thigh.

As you catch your breath, you spot a little bead of milk on one of Ava's nipples.